Add a textarea for the details meta field on WooCommerce product category terms

functions.php

<?php

add_action( 'product_cat_add_form_fields', 'wpm_product_cat_add_details_meta' );
/**
 * Add a details metabox to the Add New Product Category page.
 *
 * For adding a details metabox to the WordPress admin when
 * creating new product categories in WooCommerce.
 *
 */
function wpm_product_cat_add_details_meta() {

	wp_nonce_field( basename( __FILE__ ), 'wpm_product_cat_details_nonce' );

	?>
	<div class="form-field">
		<label for="wpm-product-cat-details"><?php esc_html_e( 'Details', 'wpm' ); ?></label>
		<textarea name="wpm-product-cat-details" id="wpm-product-cat-details" rows="5" cols="40"></textarea>
		<p class="description"><?php esc_html_e( 'Detailed category info to appear below the product list', 'wpm' ); ?></p>
	</div>
	<?php

}